The present invention relates to a process for the preparation of epoxidized synthetic cis-1,4-polyisoprene. More particularly, the present invention involves a process for the preparation of epoxidized synthetic cis-1,4-polyisoprene in an aliphatic C.sub.5 -C.sub.7 solution using tertiary butyl hydroperoxide and a particular molybdenum catalyst.
Epoxidized natural rubber has recently been commercialized and its use in various rubber products been investigated. The natural rubber may be epoxidized as a latex by the use of aqueous hydrogen peroxide. Since the epoxidized natural rubber has very selective applications due to its properties, it would be desirable to have an epoxidized form of synthetic cis-1,4-polyisoprene for applications not met by epoxidized natural rubber. Unfortunately, synthetic cis-1,4-polyisoprene is commercially produced by the catalytic polymerization of isoprene in a C.sub.5 -C.sub.7 aliphatic hydrocarbon solution. Since isolation of the polyisoprene and subsequent modification would be less practical, it would be desirable to epoxidize the polyisoprene in the C.sub.5 -C.sub.7 aliphatic hydrocarbon.
It is well known that tertiary butyl hydroperoxide has been used in the metal-catalyzed oxygenation of olefins. For example, K. Barry Sharpless et al, Aldrichimica Act, Vol. 12, No. 4, pages 63-74, (1979) disclose the use of tertiary butyl hydroperoxide in the molybdenum-catalyzed epoxidization of isolated olefins. Unfortunately, many conventional molybdenum catalysts are not readily soluble in C.sub.5 -C.sub.7 aliphatic hydrocarbons. Another problem is the undesirable degradation of the polyisoprene from the epoxidization reaction. Therefore, there exists a need for an efficient method to produce epoxidized synthetic cis-1,4-polyisoprene without the substantial degradation of the end product.